diff --git a/xen/arch/arm/include/asm/irq.h b/xen/arch/arm/include/asm/irq.h
index ec437add09..88e060bf29 100644
--- a/xen/arch/arm/include/asm/irq.h
+++ b/xen/arch/arm/include/asm/irq.h
@@ -56,7 +56,7 @@ extern const unsigned int nr_irqs;
 struct irq_desc;
 struct irqaction;
 
-struct irq_desc *__irq_to_desc(int irq);
+struct irq_desc *__irq_to_desc(unsigned int irq);
 
 #define irq_to_desc(irq)    __irq_to_desc(irq)
 
diff --git a/xen/arch/arm/irq.c b/xen/arch/arm/irq.c
index 6b89f64fd1..b9757d7ad3 100644
--- a/xen/arch/arm/irq.c
+++ b/xen/arch/arm/irq.c
@@ -48,7 +48,7 @@ void irq_end_none(struct irq_desc *irq)
 static irq_desc_t irq_desc[NR_IRQS];
 static DEFINE_PER_CPU(irq_desc_t[NR_LOCAL_IRQS], local_irq_desc);
 
-struct irq_desc *__irq_to_desc(int irq)
+struct irq_desc *__irq_to_desc(unsigned int irq)
 {
     if ( irq < NR_LOCAL_IRQS )
         return &this_cpu(local_irq_desc)[irq];